Integrated vacuum resid to chemicals conversion process

ABSTRACT

A process and apparatus for cracking a hydrocarbon feed containing resid, comprising: heating a hydrocarbon feedstock containing resid; passing said heated hydrocarbon feedstock to a vapor/liquid separator; flashing said heated hydrocarbon feedstock in said vapor/liquid separator to form a vapor phase and a liquid phase containing said resid; passing at least a portion of said resid-containing liquid phase from said vapor/liquid separator to a thermal conversion reactor operating at 649° C. or more, wherein the thermal conversion reactor contains coke particles; and converting at least a portion of said resid into olefins.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to concurrently filed application U.S. Ser.No. 12/833,556. This invention also relates to U.S. Ser. No. 12/692,222(filed Jan. 22, 2010).

FIELD OF THE INVENTION

The invention relates to a method of making olefins from a crude orresid-containing crude fraction.

BACKGROUND OF THE INVENTION

Thermal cracking of hydrocarbons is a petrochemical process that iswidely used to produce olefins such as ethylene, propylene, butylenes,butadiene, and aromatics such as benzene, toluene, and xylenes. Each ofthese is a valuable commercial product in its own right. For instance,the olefins may be oligomerized (e.g., to form lubricant basestocks),polymerized (e.g., to form polyethylene, polypropylene, and otherplastics), and/or functionalized (e.g., to form acids, alcohols,aldehydes and the like), all of which have well-known intermediateand/or end uses. One thermal cracking process is steam cracking, whichinvolves cracking hydrocarbons at elevated temperatures in the presenceof steam or gas mixtures containing steam.

Typically in steam cracking, a hydrocarbon feedstock such as naphtha,gas oil, or other non-resid containing fractions of whole crude oil,which may be obtained, for instance, by distilling or otherwisefractionating whole crude oil, is usually mixed with steam andintroduced to a steam cracker. Conventional steam cracking utilizes apyrolysis furnace that generally has two main sections: a convectionsection and a radiant section. In the conventional pyrolysis furnace,the hydrocarbon feedstock enters the less severe convection section ofthe furnace as a liquid (except for light feedstocks which enter as avapor) wherein it is heated and vaporized by indirect contact with hotflue gas from the radiant section and optionally by direct contact withsteam. The vaporized feedstock (and optional steam) mixture is thenconveyed (typically through crossover piping) into the radiant sectionwhere it is quickly heated, at pressures typically ranging from about 10to about 50 psig (69 to 345 kPa), to a severe hydrocarbon crackingtemperature, such as in the range of from about 1450° F. (788° C.) toabout 1650° F. (900° C.), to provide thorough thermal cracking of thefeedstream. The resulting products, comprising olefins, leave thepyrolysis furnace for rapid quenching and further downstream separationand processing.

After cracking, the effluent from the pyrolysis furnace contains gaseoushydrocarbons of great variety, e.g., saturated, monounsaturated, andpolyunsaturated, and can be aliphatic and/or aromatic, as well assignificant amounts of molecular hydrogen (H₂). The cracked product isthen further processed such as in the olefin production plant toproduce, as products of the plant, the various separate individualstreams of high purity, i.e., hydrogen, the light olefins ethylene,propylene, butylenes, and aromatic compounds, as well as other productssuch as pyrolysis gasoline and pyrolysis gas oils.

As worldwide demand for light olefins increases and the availability offavorable crude sources is depleted, it becomes necessary to utilizeheavier crudes (i.e., those having higher proportions of resid), whichrequires increased capital investments to process and handle therefining byproducts. It is highly desirable to have processes that cantake lower cost, heavier crudes, and produce a higher value product mixof light olefins, more efficiently. However, conventional steam crackingprocesses are known to be severely limited by fouling when usingfeedstocks containing high concentrations of resid, which is commonlypresent in low quality, heavy feeds. Thus, most steam cracking furnacesare limited to processing of higher quality feedstocks which have hadsubstantially all of the resid fraction removed in other refineryprocesses. Such additional processes increase the cost of the overallprocess. Likewise, removal of the resid fraction lowers the overallconversion efficiency of the refinery process, since most of the residfraction is mixed with low value fuel oils, rather than being convertedto higher-value materials.

Cracking of heavy hydrocarbon feeds in fluidized cokers has beendescribed in U.S. Pat. No. 3,671,424, incorporated herein by reference,which discloses a two-stage fluid coking process in which the firststage is a transfer line for short contact time and the second is eithera transfer line or a fluidized bed.

U.S. Patent Published Patent Application No. 2007/0090018, incorporatedherein by reference, discloses integration of hydroprocessing and steamcracking. A feed comprising crude or resid-containing fraction thereofis severely hydrotreated and passed to a steam cracker to obtain anolefins product.

U.S. Pat. No. 4,975,181, incorporated herein by reference, discloses animproved process and apparatus for the pyrolysis of a heavy hydrocarbonfeed utilizing a transfer line reactor wherein pyrolysis reactiontemperatures are achieved by contact of the heavy hydrocarbon feed withheated solid particles immediately followed by quenching of thepyrolysis gaseous effluent with cooled solid-particles in the transferline reactor to maximize ethylene production and minimize the effect ofsecondary reactions.

Other patents of interest related to cracking heavy feeds include U.S.Pat. No. 4,257,871; U.S. Pat. No. 4,065,379; U.S. Pat. No. 4,180,453;U.S. Pat. No. 4,210,520; U.S. Pat. No. 7,097,758; U.S. Pat. No.7,138,097; U.S. Pat. No. 7,193,123; U.S. Pat. No. 3,487,006; U.S. Pat.No. 3,617,493; U.S. Pat. No. 4,065,379; U.S. Pat. No. 3,898,299; U.S.Pat. No. 5,024,751; U.S. Pat. No. 5,413,702; U.S. Pat. No. 6,210,561;U.S. Pat. No. 7,220,887; U.S. Pat. No. 3,617,493; US 2007/023845; WO01/66672; WO 2007/117920; U.S. Pat. No. 6,632,351; WO 2009/025640; andWO 2007/117919. Other references of interest include: “Tutorial: DelayedCoking Fundamentals.” P. J. Ellis and C. A. Paul, paper 29a, TopicalConference on Refinery Processing, 1998 Great Lakes Carbon Corporation(which can be downloaded from http://www.coking.com/DECOKTUT.pdf).

There remains in the art a need for new means and processes foreconomical processing of heavy, resid-containing feeds for theproduction of olefins, aromatics, and other valuable petrochemicalproducts. All known art previous to this invention, has deficiencies,shortcomings, or undesirable aspects.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is directed to a process,preferably a continuous process, for cracking a hydrocarbon feedcontaining resid, comprising: heating a hydrocarbon feedstock containingresid; passing said heated hydrocarbon feedstock to a vapor/liquidseparator (such as a knock-out drum); flashing said heated hydrocarbonfeedstock in said vapor/liquid separator to form a vapor phase (such asan overhead vapor phase) and a liquid phase containing said resid;passing at least a portion of said resid-containing liquid phase fromsaid vapor/liquid separator to a thermal conversion reactor containingcoke particles, (preferably the thermal conversion reactor is operatingat 1200° F. (649° C.) or more); and converting at least a portion ofsaid resid into olefins. Preferably the coke particles are present inthe reactor at a coke particle/fresh feed ratio (wt/wt) of at least 1:1,based on the weight of circulating coke solids and fresh feed enteringthe reactor. (When a reactor or reaction zone is stated to be “operatingat” a certain temperature it means that material in the reactor or zonehas been heated to that temperature.) If the resid thermal conversionreactor is operated in a riser configuration, the solids circulation ispreferably adjusted to provide a hot coke/fresh resid feed ratio (wt/wt)in the contacting zone of at least 3:1, preferably above 5:1, andpreferably above 8:1, preferably up to about 30:1 preferably with shortcontacting times on the order of seconds (typically 0.5 to 30 seconds,preferably 1 to 10 seconds, preferably 1.5 to 5 seconds). If the thermalconversion unit is operating as a dense fluid bed, this ratio could besimilar or somewhat lower (such as 0.1:1 to 30:1) and include longercontacting times in the range of 10-20 seconds or more (such as 10 to 60seconds).

In another embodiment of the process, the thermal conversion reactor isa transfer line reactor integrated with a fluidized coker, and theprocess further comprises combining said resid-containing liquid bottomsphase with coke particles extracted from said fluidized coker to form afluidized mixture within said transfer line reactor.

In another embodiment, the process further comprises separating saidcoke particles from said olefins exiting said transfer line reactor withat least one cyclone separator and passing said coke particles into asteam-air gasifier incorporated within said fluidized coker.

In another embodiment, the process comprises mixing said residcontaining liquid bottoms phase with an effluent from a fluidizedcatalytic cracking (FCC) reactor containing FCC catalyst fines, prior topassing said liquid phase to said transfer line reactor.

Advantageously, the process further comprises recycling said FCCcatalyst fines and said coke particles between said transfer linereactor and said fluidized coker, such that the concentration of FCCcatalyst fines achieves a steady state level between 5 wt % and 25 wt %of the circulating solids.

Conveniently, the hydrocarbon feedstock is heated in a convectionsection of a steam cracking furnace, and said vapor/liquid separator(such as a knock-out drum) is integrated with said steam crackingfurnace.

Advantageously, said hydrocarbon feedstock contains at least 1 wt %resid, preferably at least 10 wt % resid, preferably at least 20 wt %resid, typically between 10 wt % and 50 wt % of resid. Preferably thehydrocarbon feedstock contains at least 1 wt % 566° C.⁺ resid,preferably at least 10 wt % 566° C.⁺ resid, preferably at least 20 wt %566° C.⁺ resid, typically between 10 wt % and 50 wt % of 566° C.⁺ resid.

Conveniently, said olefins are combined with a product stream from asteam cracking furnace.

Preferably, the temperature within the thermal conversion reactor isfrom 649° C. to 1000° C., preferably from 700° C. to 900° C., typicallyfrom 700° C. to 800° C.

The present invention is also directed to a system, preferablycontinuous, for cracking hydrocarbon feedstock containing residcomprising: a steam cracking furnace having a vapor/liquid separator(such as a knock-out drum) integrated with a convection section of saidfurnace; and a fluidized coker comprising: a fluidized bed gasifier, atransfer line reactor comprising a hydrocarbon feed inlet in fluidcommunication with a lower portion of said knock-out drum, and apyrolysis product outlet line, a solids conduit connecting a lowerportion of said fluidized bed gasifier with said transfer line reactor,and at least one cyclone separator having an inlet connected to saidpyrolysis product outlet line, a cracked product outlet at a top portionof said cyclone separator, and a solids outlet at the bottom of saidcyclone separator.

Advantageously, the system further comprises an air/steam inlet at thebottom of said fluidized bed gasifier.

In another embodiment, the fluidized bed coker further comprises afluidized bed heater vessel, having recirculating solids conduits,preferably two solids conduits, connecting lower portions of said heatervessel and said gasifier, and at least one gas conduit connected betweenan upper portion of said gasifier and the lower portion of said heatervessel.

Advantageously, the cyclone separator solids outlet is connected toeither or both of said fluidized bed gasifier or said heater vessel.

In one embodiment, the transfer line reactor is a vertical riserreactor, wherein said solids conduit and said hydrocarbon feed inlet areconnected to a lower portion of said reactor.

In another embodiment, the transfer line reactor is a downflow reactor,wherein said solids conduit and said hydrocarbon feed inlet areconnected to an upper portion of said reactor.

In another embodiment, C₂-C₄ hydrocarbons are produced in the thermalconversion reactor and said C₂-C₄ hydrocarbons are further converted byrecycling to a steam cracking furnace.

In another embodiment, any process described here is a continuousprocess. By continuous is meant that the process operates withoutcessation or interruption. For example, a continuous process to produceolefins would be one where the reactants are continually introduced intoone or more reactors and olefin product is continually withdrawn.

These and other objects, features, and advantages will become apparentas reference is made to the following detailed description, preferredembodiments, examples, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Figures below, similar apparatuses and/or process steps areidentified with like numbers.

FIG. 1 is a flow diagram of an embodiment of the present inventionprocess.

FIG. 2 is a diagram of a thermal conversion reactor useful in thepresent process.

DETAILED DESCRIPTION OF THE INVENTION

This invention discloses methods, preferably continuous methods, forproducing chemicals, (such as olefins and or other cracked componentssuch as lighter hydrocarbons) from heavy feedstocks in a manner where ahigh fraction of vacuum resid is more efficiently converted to chemicals(such as olefins and or other cracked components such as lighterhydrocarbons). The invention involves combination of a steam crackerhaving an integrated knock-out drum with a high temperature fluid cokeror Flexicoker™.

The fluid coking and Flexicoking™ processes were developed by Exxon inthe 1960s and are described in detail in a wide range of previouspatents as well as textbooks on resid processing technologies. Forexample, U.S. Pat. No. 3,671,424, incorporated herein by reference,describes and illustrates a suitable fluidized coking apparatus andprocess for use herein.

In an embodiment of the present invention, the resid-containing effluentfrom a knock-out drum, such as a knock-out drum which is integrated withthe convection section of a steam cracking furnace, is withdrawn as abottoms stream, passed to a thermal conversion reactor, such as afluidized coker, cracked and converted to desired products includingolefins, which can be combined with a product stream exiting the radiantsection of one or more steam crackers. The terms thermal pyrolysis unit,pyrolysis unit, steam cracker, and steamcracker are used synonymouslyherein; all refer to what is conventionally known as a steam cracker,even though the use of steam is optional.

According to the invention, a crude oil or fraction thereof containingresid is utilized as a feedstock for a steam cracking furnace. Suitablelower value feeds may typically include heavier crudes, thosehydrocarbon feedstocks that have high concentrations of resid, highsulfur, high Total Acid Number (TAN), high aromatics, and/or lowhydrogen content.

Crude, as used herein, means whole crude oil as it issues from awellhead, production field facility, transportation facility, or otherinitial field processing facility, optionally including crude that hasbeen processed by a step of desalting, treating, and/or other steps asmay be necessary to render it acceptable for conventional distillationin a refinery. Crude as used herein is presumed to contain resid.

Crude fractions are typically obtained from the refinery pipestill.Although any crude fraction obtained from the refinery pipestill may beuseful in the present invention, a significant advantage offered by thepresent invention is that crude or crude fractions still containing allor a portion of the original resid present in the whole crude obtainedfrom the wellhead may be used as feed for a steam cracker. In oneembodiment, the crude or other feedstock to the present system maycomprise at least about 1 wt % resid, preferably at least about 5 wt %resid, and more preferably at least about 10 wt % resid up to about 50wt % resid, preferably at least about 1 wt % 566° C.⁺ resid, preferablyat least about 5 wt % 566° C.⁺ resid, and more preferably at least about10 wt % 566° C.⁺ resid up to about 50 wt % 566° C.⁺ resid.

Resid as used herein refers to the complex mixture of heavy petroleumcompounds otherwise known in the art as residuum or residual.Atmospheric resid is the bottoms product produced in atmosphericdistillation where the endpoint of the heaviest distilled product isnominally 650° F. (343° C.), and is referred to as 650° F.⁺ (343° C.⁺resid. Vacuum resid is the bottoms product from a column under vacuumwhere the heaviest distilled product is nominally 1050° F. (566° C.),and is referred to as 1050° F.⁺ (566° C.⁺) resid. (The term “nominally”means here that reasonable experts may disagree on the exact cut pointfor these terms, but probably by no more than +/−50° F. or at most+/−100° F.) This 1050° F.⁺ (566° C.⁺) portion contains asphaltenes,which traditionally are considered to be problematic for the steamcracker, resulting in severe fouling and potentially corrosion orerosion of the apparatus. The term “resid” as used herein means the 650°F.⁺ (343° C.⁺) resid and 1050° F.⁺ (566° C.⁺) resid unless otherwisespecified (note that 650° F.⁺ resid comprises 1050° F.⁺ resid).According to this invention, at least a portion of the 650° F.⁺ resid,up to at least the 1050° F.⁺ (566° C.⁺) boiling point fraction, isvaporized, such as when combined with steam, and/or when the pressure isreduced or flashed in the knock-out drum of the steam cracker.

Resid typically contains a high proportion of undesirable impuritiessuch as metals, sulfur and nitrogen, as well as high molecular weight(C₁₂ ⁺) naphthenic acids (measured in terms of TAN according to ASTMD-664, TAN refers to a total acid number expressed as milligrams (“mg”)of KOH per gram (“g”) of sample). Yet another advantage of the presentinvention is that feeds high in one or more of these impurities may bereadily processed. In some embodiments, this invention can be practicedon 566° C.⁺ resid having: one or more (preferably two, three, four,five, six or seven) of the following properties: 1) 50 ppm of Ni ormore, alternately 100 ppm or more, alternately 125 ppm or more, basedupon the weight of the 566° C.⁺ resid; and/or 2) 200 ppm vanadium ormore, alternately 500 ppm or more, alternately 900 ppm or more, basedupon the weight of the 566° C.⁺ resid; and/or 3) 4 wt % sulfur or more,alternately 5 wt % or more, alternately 6 wt % or more, based upon theweight of the 566° C.⁺ resid; and/or 4) a TAN of at least 0.1,alternately at least 0.3, alternately from about 0.1 to about 20, about0.3 to about 10, or about 0.4 to about 5; and/or 5) an API gravity of 19or less (ASTM D6822, 15.5° C.); and/or 6) a C₅ asphaltenes content of atleast 0.04 grams of C₅ asphaltenes per gram of resid (“C₅ asphaltenes”refers to asphaltenes that are insoluble in pentane as determined byASTM Method D2007); and/or 7) a kinematic viscosity at 37.8° C. of atleast 10 cSt (as determined by ASTM D445). Examples resids that can beused herein are the 566° C.⁺ resids obtained from crudes including, butnot limited to, crudes from of the following regions of the world: U.S.Gulf Coast, southern California, north slope of Alaska, Canada tarsands, Canadian Alberta region, Mexico Bay of Campeche, Argentinean SanJorge basin, Brazilian Santos and Campos basins, Egyptian Gulf of Suez,Chad, United Kingdom North Sea, Angola Offshore, China Bohai Bay, ChinaKaramay, Iraq Zagros, Kazakhstan Caspian, Nigeria Offshore, Madagascarnorthwest, Oman, Netherlands Schoonebek, Venezuelan Zulia, Malaysia, andIndonesia Sumatra. Additional resids useful herein include 566° C.⁺resids obtained from crude oils described as “disadvantaged” in U.S.Pat. No. 7,678,264, incorporated by reference herein.

In a preferred embodiment, wherein the feed comprises crude oratmospheric resid that contain appreciable amounts of 1050° F.⁺ (566°C.⁺) resids, e.g., 10 wt % or more of resid, or 20 wt % or more ofresid, or even 50 wt % or more of resid, the resid-containing feed maybe passed into the convection section of a pyrolysis unit, where it isheated. Then the heated feed may be passed to a pressure reductiondevice or flash separation drum, which is integrated with the pyrolysisfurnace, to drop out the heaviest fraction (e.g., substantially theasphaltenes). The terms “flash drum”, “flash pot”, “knock-out drum” andknock-out pot” are used interchangeably herein; they are known in theart, meaning generally, a vessel or system to separate a liquid phasefrom a vapor phase. The term “flash” means generally to effect a phasechange for at least a portion of the material in the vessel from liquidto vapor, via a reduction in pressure and/or an increase in temperature.An integrated knock out drum is a vapor/liquid separator that is influid communication with a steam cracker. Specifically, the integratedknock-out drum is in fluid communication with the convection section ofa steam cracker, where feedstock is heated (optionally mixed withsuperheated steam) and transferred to said knock-out drum operating as avapor/liquid separator, thereafter the vapors from the knock-out drumare returned to the steam cracker, preferably either to the convectionor radiant section, or both. The addition of steam may further assistflash separation by reducing the hydrocarbon partial pressure, assist inconversion and vaporization of the 750° F.⁺ (399° C.⁺) to 1050° F.⁺(566° C.⁺) (preferably even a substantial portion of the 1100° F.⁺ (593°C.⁺)) resid fractions, and prevent fouling.

Preferred flash drums or vapor/liquid separation devices, and theirintegration with pyrolysis units have previously been described in U.S.Pat. Nos. 7,090,765, 7,097,758, and 7,138,097, which are incorporatedherein by reference. Another apparatus effective as a flash drum forpurposes of the present invention is described in U.S. Pat. No.6,632,351 as a “vapor/liquid separator”.

The vapor/liquid separator operates at a temperature and pressure wherethose portions of the feed material that cause coking are kept in aliquid state, preferably the vapor/liquid separator operates at atemperature of between about 375 to 525° C., preferably from 400 to 500°C., preferably from 800° F. (about 425° C.) and about 870° F. (about465° C.), but also typically not over about 900° F. (about 482° C.).Flashing material through the flash drum to obtain an overhead vapor andliquid bottoms further facilitates vaporization of a major fraction ofthe 650° F.⁺ (343° C.⁺) to 1050° F.⁺ (566° C.⁺) fraction of the resids.

A steam cracking furnace (also referred to as a “steam cracker”) is apyrolysis furnace that has two main sections: a convection section and aradiant section, where hydrocarbon feedstock enters the less severeconvection section of the furnace as a liquid (except for lightfeedstocks which enter as a vapor) and where the feedstock is heated andvaporized by indirect contact with hot flue gas from the radiant sectionand optionally by direct contact with steam. The vaporized feedstock andsteam mixture (if present) is then introduced (typically throughcrossover piping) into the radiant section where it is quickly heated,at pressures typically ranging from about 10 to about 50 psig (69 to 345kPa), to a severe hydrocarbon cracking temperature, such as in the rangeof from about 1450° F. (788° C.) to about 1650° F. (900° C.), to providethorough thermal cracking of the feedstream. The resulting productstypically comprise olefins.

Steam cracking alone provides for a product comprising significantyields of fuel oil, tar, and non-aromatic SCN (steam cracked naphtha) inaddition to the desired ethylene, propylene, butylenes, C₅ olefins,dienes, and single-ring aromatic products. However, in a processaccording to the present invention, steam cracking conductedsimultaneously and in parallel with another high temperature thermalconversion reactor, such as a coker, reduces the yields of fuel oil,while increasing the yield of the aforementioned desirable petrochemicalproducts. By separating a resid-containing bottoms liquid in thevapor/liquid separator, and then cracking the resid in a fluidizedcoker, further improvement in the conversion of resid components tovaporized chemical precursors, such as light olefins and other morevaluable light products can be achieved.

The fluid coker preferably includes an integrated air gasifier (orpartial oxidation reactor) which is used to convert coke to fuel gas bysteam/air gasification and combustion at between about 1400-1800° F.(760-982° C.). This gasification can be facilitated by cofeeding oxygenor by using oxygen enriched air. Hot, partially gasified coke from thisgasification reaction is continuously withdrawn from the gasifier andfed to one or more solids transfer lines where it is contacted with thebottoms material recovered from one or more steam cracking furnacesequipped with integrated vapor/liquid separators (such as knock-outdrums). This residual oil fraction is converted at 1300-1800° F.(704-982° C.) to a mixture of lighter hydrocarbons containing highconcentrations of ethylene and propylene. While the transfer linereactors can be configured in several ways, a preferred configuration issimilar to that used in fluid catalytic cracking units; e.g., thetransfer line is operated as a vertical riser reactor where the hotsolids are contacted with feed near the bottom of the riser, the solidsand vapor are transported upward along the riser, and the solids andvapor are separated using one or more cyclones in series. Alternatively,the transfer line can be operated as “downer” or downflow reactor.Irrespective of the specific configuration, the transfer line reactor ishighly effective for contacting hot coke with the residual oil. The hotcoke provides the heat needed to fully convert the residual oil feed tolighter hydrocarbons in short reaction times of about 0.1-10 seconds,preferably about 1 second, and to coke which is deposited on previouslyformed coke particles.

Alternately, the thermal conversion reactor, preferably a transfer linereactor, contains at least 0.1 wt % coke particles, based upon theweight of the circulating solids in the thermal conversion reactor,preferably 1 to 30 wt %, preferably from 3 to 25 wt %, preferably from 5to 25 wt %.

A primary feature of the present invention is the direct use of hotgasifier coke as a heat transfer medium for high temperature coking ofresidual oil for producing chemicals. This embodiment differssubstantially from prior art related to the fluid coking processes. Theinventors have unexpectedly discovered that high temperature coking iseffective for producing chemicals (such as olefins and or other crackedcomponents such as lighter hydrocarbons), especially when integratedwith a steam cracker equipped with integrated vapor/liquid separators(such as knock-out drums).

In the figures and description below, reference to a knock-out drum maybe taken to generally refer to any vapor/liquid separator device.

The basic flow scheme is illustrated in FIG. 1. A heavy feedstock 100containing 1 wt % or more (typically about 10-50 wt %) molecules boilingin the vacuum resid range (566° C.⁺) is fed to a first steam crackingfurnace 200 which includes an integrated knock-out drum 205. The wholefeed is heated to about 400-470° C. in the convection section 206 of thefurnace. The whole feed passes through line 207 into the knock-out drumseparation device 205 where molecules boiling below about 538-593° C.are vaporized (or remain vaporized) and are separated from heaviercompounds which remain in the liquid phase (pressure reduction and/orsteam stripping, among other things, in the drum can be used to causeadditional molecules to vaporize). Material typically enters the drum ata temperature of about 400-470° C. and vaporization is facilitated bythe use of steam stripping or stripping with light hydrocarbons. Thevapors pass through line 210 into the radiant section 250 of the firststeam cracking furnace 200 (either directly or via a heater, such atransfer line heater or a convection section of the steam cracker),whereas the heavy liquids are withdrawn from the bottom of the knock-outdrum through line 220.

This material that is removed from the bottom of the knock-out drum thenserves as the primary feedstock for the high temperature cokingapparatus 300. Heavy liquids from several knock-out drum equippedfurnaces are preferably combined to achieve better economy of scale inthe high temperature fluid coker process. If the unit is located in alarge refinery complex, it is possible to combine supplemental residualoil feedstock 230 from the refinery with that recovered from theknock-out drums. Another potential feedstock from the steam cracker isthe heavy fractions (or steam cracked tar) produced from steam crackingof gas oil fractions.

In another preferred embodiment, products from the steam crackingreaction 252 are combined with hydrocarbon products from the hightemperature coking reaction 310 before separation into a series of fueland chemical products such as olefins and or other cracked componentssuch as lighter hydrocarbons). In this manner, better energy efficiencyand economy of scale is achieved in the separation process. This can beaccomplished by cooling the vapors from the steam cracking and cokingreactions by contacting with quench oils and/or use of heat exchangers.The cooled vapors and any condensed liquids are fed to a common primaryfractionator 400 where the wide-cut product is separated into severalmajor product streams 410 such as C₄ ⁻ hydrocarbons, C₅-C₁₀ naphtha,C₁₀-C₂₀ distillates, and heavier gas oils. (C₄ ⁻ hydrocarbons are gaseswith weights at or below C₄, including methane, ethane, ethylene,propylene, propane, butenes, butanes, hydrogen, and the like.) Thesemajor product streams are then further separated and purified usingtypical methods for the refining and chemicals industry such asfractionation and hydroprocessing. Fuel gas (CO, CO₂ and H₂) createdduring the high temperature coking process is withdrawn from the coker300 via line 320 and/or 346 for use elsewhere in the process, describedbelow. One of the important advantages of the integrated coking andsteam cracking configuration is that light paraffins, such as ethane andpropane that are produced in the coking reaction, can be easily recycledto one of the steam cracking furnaces for conversion to ethylene andpropylene.

In a preferred embodiment, the residual oil feedstock to the hightemperature coking reactor is mixed with minor amounts of heavy cycleoil (HCCO) 215 from a fluid cat cracking (FCC) process. The heavy cycleoil normally boils in the range of about 454 to 593° C. and normallycontains small levels (0.01 to 2-3 wt %) of FCC catalyst fines. Thesefines are produced by attrition of FCC catalyst particles during the FCCprocess. By adding a small amount of HCCO containing FCC catalyst finesto the high temperature coking process, it is possible to introduce amodest level of catalytic boost to the resid coking process which iseffective for increasing the yield of propylene in the product mixturefrom high temperature coking. Because the high temperature cokeroperates in a cyclic manner, described in more detail below, where thecoke particles are circulated between the gasifier, heater, and reactor,multiple passes are required before the coke particles are fullyconverted or otherwise removed as purge. Therefore, it is possible tobuild a moderately high concentration (5-25 wt %) of catalyst fines intothe circulating solids inventory.

FIG. 2 provides a simplified diagram to further illustrate the processand apparatus for high temperature coking. The fluidized coker 300includes an air gasifier 340 which operates as a dense phase fluidizedbed reactor at about 871-1037° C., preferably about 954° C. Air andsteam 342 are fed to the gasifier using a series of distributors ornozzles which are incorporated in a grid plate 345 within the gasifier.The reaction of air and steam with the coker particles converts part ofthe coke to a mixture of gases primarily including CO, CO₂, H₂ (fuelgas). The coke partial oxidation reaction which occurs in the gasifieris exothermic and produces the heat needed to drive the endothermiccoking reaction. Energy balance is achieved by balancing the rates atwhich air and steam are fed to the gasifier with the rate of cokeremoval through solids line 333 for use in the coking reaction, the feedrate to the coker, and coke withdrawal to the “heater” vessel 350through line 348, and processing temperatures within the differentsections of the unit. Slide valves or other means can be used to adjustthe solids circulation rates and pressure balance within the system.

Residual oil from the steam cracker integrated knock-out drum and/orother refinery resid-containing feed 220/230 is fed to one or moretransfer line reactors 330 which are supplied with hot circulating cokefrom the air gasifier 340 through line 333. The heavy oil is convertedin the transfer line reactor (such as a riser or standpipe), exitsthrough line 305, and the cracked vapors 310 are separated from thesolids using cyclones 335 (or other separation devices) and optionallystripping with steam or other process gas. In addition to crackedproducts, the coking reaction converts part of the feedstock (typically15-40%) to new coke deposits on the coke particles. As shown, coke isremoved from the cracked gas and returned to the gasifier 340 throughline 315, where it is further converted by air gasification.Alternatively, in another embodiment (not shown), it may be preferred todisengage the cracked vapor from the solid coke particles above theheater vessel 350, rather than to disengage the coke particles back intothe gasifier. The decision whether to disengage coke into the heater orthe gasifier is determined by the specific unit design, the gasifieroperating pressure, and operating features such as the feed quality orcrackability. Both approaches are fully feasible and fall within theoverall scope of the invention. In both approaches it will beadvantageous to steam strip the coke to increase recovery of crackedproducts.

Product gas 346 from the gasifier is removed overhead from the gasifier340 directly or more typically by routing to the heater for partialcooling and collection overhead using internal cyclones and suitablepiping. The processing unit includes at least another fluidized bedlabeled as the heater 350. This vessel can have several functions withthe primary role to partially cool the gasifier product gases (as notedabove) and moderate and maintain overall heat balance and solidscirculation. Hot solid coke particles are circulated between thegasifier 340 and the heater 350 using solids transfer lines 348 and 352.

The heater is maintained at a much lower average bed temperature ascompared to the gasifier, typically 315-537° C. Hot product fuel gas 346from the gasifier 340 is routed to the heater 350 where it is cooled toapproximately the heater operating temperature. This gas and optionallysteam are used to fluidize the coke within the heater 350. The cooledfuel gas 320 has medium BTU content and can be subsequently used as fuelfor furnaces or power generating equipment within the refinery orchemical plant. It is also possible to use the heater for preheating theresidual oil feed to the coking reaction. This can be accomplished usingheat exchangers within the vessel (not shown). Likewise, it is alsopossible to remove part of the coke from the heater as a purge stream355. This is particularly useful to improve operating efficiency whenthe feed to the coking reaction has higher metal or mineral content.

While this second vessel can be helpful in improving unit energyefficiency and operability, it is also possible to design a unit with asingle vessel so as to reduce investment and operating complexity. Oneof the major advantages of the fluid coking process for producingchemicals from heavy residual oils is the ability to utilize lowerquality feeds which may contain metals or other forms of mineral matterwith a high degree of flexibility. Other known processes, such as hightemperature catalytic cracking or catalytic pyrolysis are not able toeffectively utilize such feeds.

Those skilled in the art of heavy feed processing are familiar with thedifficulties of operating heavy feed steam cracking and coking processeswithout fouling. It is not obvious how to integrate the processeswithout further aggravating these phenomena. The integrated knock-outdrum is particularly efficient and effective in this regard, as itallows cut points between the vapor and heavy liquids to be easilyvaried consistent with the properties of the feedstock.

In another embodiment, this invention relates to:

1. A process for cracking a hydrocarbon feed containing resid,comprising:

(a) heating a hydrocarbon feedstock containing resid;

(b) passing said heated hydrocarbon feedstock to a vapor/liquidseparator (such as a knock-out drum);

(c) flashing said heated hydrocarbon feedstock in said separator to forma vapor phase (typically an overhead vapor phase) and a liquid phase(such as a liquid bottoms phase) containing said resid;

(d) passing at least a portion of said resid-containing liquid bottomsphase from said separator to a thermal conversion reactor where theresid-containing liquid bottoms phase is heated to 649° C. or more,wherein said thermal conversion reactor contains coke particles, saidreactor having a coke particle/fresh feed ratio (wt/wt) of at least 1:1(preferably at least 3:1, preferably at least 5:1, alternately from 1:1to 50:1, preferably from 3:1 to 30:1), based on the weight ofcirculating coke solids and fresh feed entering the reactor; and

(e) converting at least a portion of said resid into olefins.

2. The process of paragraph 1, wherein said thermal conversion reactoris a transfer line reactor and the coke particle/fresh feed ratio(wt/wt) in the transfer line reactor is in the range of about 3:1 toabout 30:1.

3. The process of paragraph 1 or 2, wherein said thermal conversionreactor is a transfer line reactor in fluid communication with afluidized coker, and further comprising combining said resid-containingliquid phase with coke particles extracted from said fluidized coker toform a fluidized mixture within said transfer line reactor.4. The process of paragraph 1, 2 or 3, further comprising separatingsaid coke particles from said olefins exiting said transfer linereactor, preferably with at least one cyclone separator, and passingsaid coke particles into a steam-air gasifier incorporated within saidfluidized coker.5. The process of any of paragraphs 1 to 4, further comprising mixingsaid resid-containing liquid phase with an effluent from a fluidizedcatalytic cracking (FCC) reactor containing FCC catalyst fines, prior topassing said liquid phase to said transfer line reactor.6. The process of paragraph 5, further comprising recycling said FCCcatalyst fines and said coke particles between said transfer linereactor and said fluidized coker, such that the concentration of FCCcatalyst fines achieves a steady state level between 5 wt % and 25 wt %of the circulating solids.7. The process of any of paragraphs 1 to 6, wherein said hydrocarbonfeedstock is heated in a convection section of a steam cracking furnace,and said separator is in fluid communication (e.g., integrated) withsaid steam cracking furnace.8. The process of any of paragraphs 1 to 7, wherein said hydrocarbonfeedstock contains between 10 wt % and 50 wt % of 566° C.⁺ resid.9. The process of any of paragraphs 1 to 8, wherein the temperaturewithin the thermal conversion reactor is from 600 to 900° C.,alternately 700 to 800° C.10. A system for cracking hydrocarbon feedstock containing residcomprising:

(a) a steam cracking furnace having a vapor/liquid separator (e.g., aknock-out drum) in fluid communication (e.g., integrated) with saidfurnace (typically the convection section of said furnace); and

(b) a fluidized coker comprising:

-   -   i) a fluidized bed gasifier,    -   ii) a transfer line reactor comprising a hydrocarbon feed inlet        in fluid communication with a lower portion of said separator,        and a pyrolysis product outlet line,    -   iii) a solids conduit connecting a lower portion of said        fluidized bed gasifier with said transfer line reactor, and    -   iv) at least one cyclone separator having an inlet connected to        said pyrolysis product outlet line, a cracked product outlet at        a top portion of said cyclone separator, and a solids outlet at        the bottom of said cyclone separator.        11. The system of paragraph 10, further comprising an air/steam        inlet at the bottom of said fluidized bed gasifier.        12. The system of paragraph 10 or 11, wherein said fluidized        coker further comprises a fluidized bed heater vessel, having        recirculating solids conduits connecting lower portions of said        heater vessel and said gasifier, and at least one gas conduit        connected between an upper portion of said gasifier and the        lower portion of said heater vessel.        13. The system of any of paragraphs 10 to 12, wherein said        cyclone separator solids outlet is connected to either or both        of said fluidized bed gasifier or said heater vessel.        14. The system of any of paragraphs 10 to 13, comprising two        solids conduits connecting lower portions of said heater vessel        and said gasifier.        15. The system of any of paragraphs 10 to 14, wherein said        transfer line reactor is a vertical riser reactor, wherein said        solids conduit and said hydrocarbon feed inlet are connected to        a lower portion of said reactor.        16. The system of any of paragraphs 10 to 15, wherein said        transfer line reactor is a downflow reactor wherein said solids        conduit and said hydrocarbon feed inlet are connected to an        upper portion of said reactor.        17. The process of any of paragraphs 1 to 8, wherein said        olefins are combined with a product stream from a steam cracking        furnace.        18. The process of any of paragraphs 1 to 8 or 17, wherein C₂-C₄        hydrocarbons are produced in the thermal conversion reactor and        said C₂-C₄ hydrocarbons are further converted by recycling to a        steam cracking furnace.        19. The system of any of paragraphs 10 to 15, wherein C₂-C₄        hydrocarbons are produced in the fluidized coker and said C₂-C₄        hydrocarbons are further converted by recycling to the steam        cracking furnace.        20. The process of any of paragraphs 1 to 8, 17 or 18, wherein        oxygen or oxygen-enriched air is introduced into the steam-air        gasifier.        21. The system of any of paragraphs 10 to 15, or 19, wherein        oxygen or oxygen-enriched air is introduced into the fluidized        bed gasifier.        22. The process of any of paragraphs 1 to 8, 17, 18 or 20, where        the coke particles are entrained in the fluid in the reactor.        23. The process or system of any of the above paragraphs 1 to        21, wherein the resid is a 566° C.⁺ resid obtained from crudes        from one or more of the following regions of the world: U.S.        Gulf Coast, southern California, north slope of Alaska, Canada        tar sands, Canadian Alberta region, Mexico Bay of Campeche,        Argentinean San Jorge basin, Brazilian Santos and Campos basins,        Egyptian Gulf of Suez, Chad, United Kingdom North Sea, Angola        Offshore, China Bohai Bay, China Karamay, Iraq Zagros,        Kazakhstan Caspian, Nigeria Offshore, Madagascar northwest,        Oman, Netherlands Schoonebek, Venezuelan Zulia, Malaysia, and        Indonesia Sumatra.

Unless otherwise specified, the meanings of terms used herein shall taketheir ordinary meaning in the art; reference shall be taken, inparticular, to Handbook of Petroleum Refining Processes, Third Edition,Robert A. Meyers, Editor, McGraw-Hill (2004). In addition, all prioritydocuments, patents and patent applications, test procedures (such asASTM methods), and other documents cited herein are fully incorporatedby reference to the extent such disclosure is not inconsistent with thisinvention and for all jurisdictions in which such incorporation ispermitted. Also, when numerical lower limits and numerical upper limitsare listed herein, ranges from any lower limit to any upper limit arecontemplated.

The invention has been described above with reference to numerousembodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

1. A process for cracking a hydrocarbon feed containing resid,comprising: (a) heating a hydrocarbon feedstock containing resid; (b)passing said heated hydrocarbon feedstock to a vapor/liquid separator;(c) flashing said heated hydrocarbon feedstock in said separator to forma vapor phase and a liquid bottoms phase containing said resid; (d)passing at least a portion of said resid-containing liquid bottom phasefrom said separator to a thermal conversion reactor where theresid-containing liquid bottoms phase is heated to 649° C. or more,wherein said thermal conversion reactor contains coke particles, saidreactor having a coke particle/fresh feed ratio (wt/wt) of at least 1:1,based on the weight of circulating coke solids and fresh feed enteringthe reactor; and (e) converting at least a portion of said resid intoolefins; (f) mixing said resid-containing liquid bottoms phase with aneffluent from a fluidized catalytic cracking (FCC) reactor containingFCC catalyst fines, prior to passing said liquid bottoms phase to saidthermal reactor wherein the concentration of FCC catalyst fines achievesa steady state level between 5 wt. % and 25 wt. % of the circulatingsolids.
 2. The process of claim 1, wherein said thermal conversionreactor is a transfer line reactor and the coke particle/fresh feedratio (wt/wt) in the transfer line reactor is in the range of about 3:1to about 30:1.
 3. The process of claim 1, wherein said thermalconversion reactor is a transfer line reactor in fluid communicationwith a fluidized coker, and further comprising combining saidresid-containing liquid bottoms phase with coke particles extracted fromsaid fluidized coker to form a fluidized mixture within said transferline reactor.
 4. The process of claim 3, further comprising separatingsaid coke particles from said olefins exiting said transfer line reactorand passing said coke particles into a steam-air gasifier incorporatedwithin said fluidized coker.
 5. The process of claim 1, wherein saidhydrocarbon feedstock is heated in a convection section of a steamcracking furnace, and said vapor/liquid separator is in fluidcommunication with said steam cracking furnace.
 6. The process of claim1, wherein said hydrocarbon feedstock contains between 10 wt % and 50 wt% of 566° C.⁺ resid.
 7. The process of claim 1, wherein said olefins arecombined with a product stream from a steam cracking furnace.
 8. Theprocess of claim 1, wherein the temperature within the thermalconversion reactor is 700° C. to 800° C.
 9. The process of claim 1,wherein the resid is a 566° C.⁺ resid having a TAN of at least 0.1. 10.The process of claim 1, wherein the resid is a 566° C.⁺ resid having aC₅ asphaltenes content of at least 0.04 grams of C₅ asphaltenes per gramof resid.
 11. The process of claim 1, wherein the resid is a 566° C.⁺resid obtained from crudes from one or more of the following regions ofthe world: U.S. Gulf Coast, southern California, north slope of Alaska,Canada tar sands, Canadian Alberta region, Mexico Bay of Campeche,Argentinean San Jorge basin, Brazilian Santos and Campos basins,Egyptian Gulf of Suez, Chad, United Kingdom North Sea, Angola Offshore,China Bohai Bay, China Karamay, Iraq Zagros, Kazakhstan Caspian, NigeriaOffshore, Madagascar northwest, Oman, Netherlands Schoonebek, VenezuelanZulia, Malaysia, and Indonesia Sumatra.
 12. The process of claim 1,wherein C₂-C₄ hydrocarbons are produced in the thermal conversionreactor and said C₂-C₄ hydrocarbons are further converted by recyclingto a steam cracking furnace.
 13. The process of claim 4, wherein oxygenor oxygen-enriched air is introduced into the steam-air gasifier. 14.The process of claim 4, where at least one cyclone separator is used toseparate said coke particles from said olefins exiting said transferline reactor.
 15. A process for cracking a hydrocarbon feed containingresid, comprising: (a) heating a hydrocarbon feedstock containing from10 wt. % to 50 wt. % of 566° C.+ resid; (b) passing said heatedhydrocarbon feedstock to a vapor/liquid separator; (c) flashing saidheated hydrocarbon feedstock in said separator to form a vapor phase anda liquid bottom phase containing said resid; (d) passing at least aportion of said resid-containing liquid bottom phase from said separatorto a transfer line reactor where the resid-containing liquid bottomsphase is heated to 649° C. or more, said reactor having a cokeparticle/fresh feed ratio (wt/wt) in the reactor of about 3:1 to about30:1; and (e) converting at least a portion of said resid into olefins;(f) mixing said resid-containing liquid bottoms phase with an effluentfrom a fluidized catalytic cracking (FCC) reactor containing FCCcatalyst fines, prior to passing said liquid bottoms phase to saidthermal reactor wherein the concentration of FCC catalyst fines achievesa steady state level between 5 wt. % and 25 wt. % of the circulatingsolids.
 16. The process of claim 15, wherein the transfer line reactoris in fluid communication with a fluidized coker, and further comprisingcombining said resid-containing liquid bottoms phase with coke particlesextracted from said fluidized coker to form a fluidized mixture withinsaid transfer line reactor.
 17. The process of claim 16, furthercomprising separating said coke particles from said olefins exiting saidtransfer line reactor and passing said coke particles into a steam-airgasifier incorporated within said fluidized coker.
 18. The process ofclaim 17, wherein said hydrocarbon feedstock is heated in a convectionsection of a steam cracking furnace, and said vapor/liquid separator isin fluid communication with said steam cracking furnace.
 19. The processof claim 15, wherein the transfer line reactor is operating at 700° C.to 800° C.
 20. The process of claim 15, wherein the resid is a 566° C.⁺resid having a TAN of at least 0.1.
 21. The process of claim 15, whereinthe resid is a 566° C.⁺ resid having a C₅ asphaltenes content of atleast 0.04 grams of C₅ asphaltenes per gram of resid.
 22. The process ofclaim 1 where the coke particles are entrained in the fluid in thereactor.
 23. A process for cracking a hydrocarbon feed containing resid,comprising: (a) heating a hydrocarbon feedstock containing from 10 wt. %to 50 wt. % of 566° C.+ resid having a TAN of at least 0.1 and a C5asphaltenes content of at least 0.04 grams of C5 asphaltenes per gramofresid in a convection section of a steam cracking furnace; (b) passingsaid heated hydrocarbon feedstock to a vapor/liquid separator in fluidcommunication with said steam cracking furnace; (c) flashing said heatedhydrocarbon feedstock in said separator to form a vapor phase and aliquid bottoms phase containing said resid; (d) passing at least aportion of said resid-containing liquid phase from said separator to a atransfer line reactor operating at 700 to 800° C. or more and the cokeparticle/fresh feed ratio (wt/wt) in the transfer line reactor is in therange of about 3:1 to about 30:1; and (e) converting at least a portionof said resid into olefins; (f) mixing said resid-containing liquidbottoms phase with an effluent from a fluidized catalytic cracking (FCC)reactor containing FCC catalyst fines, prior to passing said liquidbottoms phase to said transfer line reactor wherein the concentration ofFCC catalyst fines achieves a steady state level between 5 wt. % and 25wt. % of the circulating solids.